1. Field of the Invention
This invention relates to novel fluorine-modified acid anhydrides suitable for use in the manufacture of epoxy resin compositions for encapsulating semiconductor devices.
2. Prior Art
Heretofore, epoxy resins have been widely utilized in various molding materials, powder coating materials, electrically insulating materials, and other engineering materials by blending them with curing agents and inorganic fillers to form epoxy resin compositions. Currently, epoxy resins find a great demand as semiconductor device encapsulating compositions since they are generally excellent in molding, adhesion, electrical properties, mechanical properties, and moisture resistance as compared with other conventional thermosetting resins.
Recently, the semiconductor device encapsulation technique is on a transition from the conventional transfer molding technique to a new encapsulation technique using liquid epoxy resin compositions. In such compositions, acid anhydrides are often used as a curing agent.
Conventional acid anhydrides used as a curing agent for liquid or transparent epoxy resins, however, are generally hygroscopic and less flexible, leaving some problems. For example, in a solder crack test of dipping encapsulated semiconductor device packages in solder after moisture absorption, cracks often occur in the packages. Also during the step of encapsulating semiconductor elements and during a thermal cycling test on encapsulated semiconductor devices, package cracks occur or excess stresses are exerted to deform the elements, causing a function lowering or failure.
Regarding these problems, the same assignee as the present invention previously proposed an epoxy resin composition having an organopolysiloxane blended in a curable epoxy resin in Japanese Patent Application Kokai (JP-A) No. 129246/1981 and an epoxy resin composition having a block copolymer of an aromatic polymer and an organopolysiloxane added to a curable epoxy resin in JP-A 21417/1983. These epoxy resin compositions were improved in crack resistance.
Nevertheless, increasingly strict requirements are now imposed on semiconductor device encapsulating materials. There is a desire to have an epoxy resin composition which is further improved in crack resistance. Especially for liquid or transparent epoxy resins, it is desired to use acid anhydrides which are more water repellent and flexible as a curing agent.